1. Field of the Invention
The present invention relates to a method for interconnecting multiple printed circuit boards, and more particularly to a method for interconnecting a plurality of orthogonally arranged printed circuit boards.
2. Description of Related Art
Various electronic systems, especially a telecommunication system, servers and switches, comprise a wide array of components mounted on printed circuit boards, such as daughterboards and motherboards. The motherboard to which the daughterboards are connected are generally referred to as backplane as it is stationary. Connectors used to assemble the daughterboards, which are removable, to the motherboards are referred to as backplane connectors. The motherboard and the daughterboard are interconnected by the connectors so as to transfer signals and power throughout the systems.
Typically, the motherboard, backplane, is a printed circuit board that is mounted in a server or a switch and is provided with a plurality of backplane connectors. Multiple daughterboards are also each provided with a mating connector and then removeably plugged into the connectors on the backplane. After all the daughterboards are interconnected to the backplane, the daughterboards are interconnected through the backplane and are arranged parallel to each other.
However, connecting the daughterboards via the backplane leads to the potential for signal interference. Because the daughterboards are all connected via the backplane, signal strength may be attenuated as signals travel through the backplane. In general, signals passing between two daughterboards pass through at least a first connector pair between a first daughterboard and the backplane, and a second connector pair between the backplane and a second daughterboard. In general, the signal passes through totally two pairs of mated connectors, and each time the signal is attenuated as it passes.
Generally, the arrangement between the backplane and the daughterboard can be referred to as a “TTTT” type viewed from atop, i.e. the backplane is arranged in a horizontal direction, while the daughterboard is arranged in a position perpendicular to the backplane. In some cases, both sides of the backplane are all provided with connectors for assembling the daughterboards from both sides. This arrangement can be referred to as a “++++” type viewed from atop. In this arrangement, the daughterboards arranged in both sides are in communication with each other through the motherboard, i.e. centerplane.
Many connectors have been provided for achieving such arrangement. U.S. Pat. No. 5,993,259 (the '259 patent) issued to Stokoe et al. discloses an electrical connector of such application. The connector disclosed in the '259 patent includes a plurality of modularized wafers bounded together. As shown in FIG. 4 of the '259 patent, the terminals are stamped from a metal sheet and then embedded within an insulative material to form the wafer.
U.S. Pat. No. 6,083,047 issued to Paagman discloses an approach to make a high-density connector by introducing the use of printed circuit boards. Conductive traces are formed on surfaces of the printed circuit board in a mirror-image arrangement, typically shown in FIG. 12.
U.S. Pat. No. 6,267,604 issued to Mickievicz et al. discloses a similar configuration.
U.S. Pat. No. 5,356,301 issued to Champion et al. discloses a pair of back-to-back arranged plug connectors mounted on opposite sides of a motherboard via common contacts for respectively connecting with a receptacle connector mounted on a daughterboard and a cable connector.
However, all connectors suggested above are all mounted on the backplane or centerplane. As it is well known that if the centerplane can be eliminated such that the daughterboards can be directly interconnected with each other, then the signal attenuation as well as the interference can be largely reduced. However, none of the connectors provided yet meets such a requirement.
U.S. Pat. No. 6,540,522 (the '522 patent) issued to Sipe sheds light on eliminating the centerplane, i.e. two daughterboards can be interconnected orthogonally, as clearly shown in FIG. 9. This is really a leap step.
However, the signal still travels a long distance from one end of a first connector on a first circuit board, to a second connector on a second circuit board. This signal attenuation is still left unsolved. On the other hand, all these above mentioned connectors could be mounted on a single side and along an edge of the motherboard as well as the daughterboards. As shown in FIG. 9 of the '522 patent, it is impossible to install a second set connectors on the opposite side of the boards.
Traditionally, if a contact defines a longitudinal direction, then a mating direction of an electrical component, i.e. a mating contact of a complementary connector or a conductive pad of a printed circuit board has to be the same direction as the contact. Before the present invention, it is impossible to insert a card into a card-edge connector where the insertion direction of the card is orthogonal to the contact within the connector. If the contacts are not well arranged, the insertion of the card will collapse the contacts within the connector. The contacts have to be retracted behind a mating face of the connector during the insertion of the card, and then extend beyond the mating face after the card arrives to its final position. None of the existing connectors meets such a requirement.
For example, U.S. Pat. No. 6,508,675, assigned to the same assignee with this patent application, discloses a configuration providing the shortest electrical path between two orthogonally arranged printed circuit boards. It can be easily appreciated, as shown in FIGS. 1 and 2, that if the printed circuit board is not inserted into a slot of a connector along a top-to-bottom direction, i.e. a vertical direction, viewed from the drawings, contact portions of contacts extending into the slot will surely be damaged by the insertion of the circuit board.
In order to let the circuit board be inserted into the slot from a direction other than the top-to-bottom direction, a mechanism has to be invented to control the contact such that the contact is retracted behind the mating face when the printed circuit board is inserted and extends over the mating face after the printed circuit board is finally positioned.
The present invention aims to provide an improved method for interconnecting multiple printed circuit boards to solve the above-mentioned problems.